/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.hbase.regionserver;

import java.io.IOException;
import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.util.ArrayList;
import java.util.List;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellComparator;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.ClassSize;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;

/**
 * The MemStore holds in-memory modifications to the Store.  Modifications
 * are {@link Cell}s.  When asked to flush, current memstore is moved
 * to snapshot and is cleared.  We continue to serve edits out of new memstore
 * and backing snapshot until flusher reports in that the flush succeeded. At
 * this point we let the snapshot go.
 *  <p>
 * The MemStore functions should not be called in parallel. Callers should hold
 *  write and read locks. This is done in {@link HStore}.
 *  </p>
 *
 * TODO: Adjust size of the memstore when we remove items because they have
 * been deleted.
 * TODO: With new KVSLS, need to make sure we update HeapSize with difference
 * in KV size.
 */
@InterfaceAudience.Private
public class DefaultMemStore extends AbstractMemStore {
    private static final Logger LOG = LoggerFactory.getLogger(DefaultMemStore.class);

    public final static long DEEP_OVERHEAD = ClassSize.align(AbstractMemStore.DEEP_OVERHEAD);
    public final static long FIXED_OVERHEAD = ClassSize.align(AbstractMemStore.FIXED_OVERHEAD);

    /**
     * Default constructor. Used for tests.
     */
    public DefaultMemStore() {
        this(HBaseConfiguration.create(), CellComparator.getInstance(), null);
    }

    /**
     * Constructor.
     * @param c Comparator
     */
    public DefaultMemStore(final Configuration conf, final CellComparator c) {
        super(conf, c, null);
    }

    /**
     * Constructor.
     * @param c Comparator
     */
    public DefaultMemStore(final Configuration conf, final CellComparator c, final RegionServicesForStores regionServices) {
        super(conf, c, regionServices);
    }

    /**
     * Creates a snapshot of the current memstore.
     * Snapshot must be cleared by call to {@link #clearSnapshot(long)}
     */
    @Override
    public MemStoreSnapshot snapshot() {
        // If snapshot currently has entries, then flusher failed or didn't call
        // cleanup.  Log a warning.
        if(!this.snapshot.isEmpty()) {
            LOG.warn("Snapshot called again without clearing previous. " + "Doing nothing. Another ongoing flush or did we fail last attempt?");
        } else {
            this.snapshotId = EnvironmentEdgeManager.currentTime();
            if(!getActive().isEmpty()) {
                // Record the ImmutableSegment' heap overhead when initialing
                MemStoreSizing memstoreAccounting = new NonThreadSafeMemStoreSizing();
                ImmutableSegment immutableSegment = SegmentFactory.instance().
                        createImmutableSegment(getActive(), memstoreAccounting);
                // regionServices can be null when testing
                if(regionServices != null) {
                    regionServices
                            .addMemStoreSize(memstoreAccounting.getDataSize(), memstoreAccounting.getHeapSize(), memstoreAccounting.getOffHeapSize(),
                                    memstoreAccounting.getCellsCount());
                }
                this.snapshot = immutableSegment;
                resetActive();
            }
        }
        return new MemStoreSnapshot(this.snapshotId, this.snapshot);
    }

    @Override
    public MemStoreSize getFlushableSize() {
        MemStoreSize mss = getSnapshotSize();
        return mss.getDataSize() > 0 ? mss : getActive().getMemStoreSize();
    }

    @Override
    protected long keySize() {
        return getActive().getDataSize();
    }

    @Override
    protected long heapSize() {
        return getActive().getHeapSize();
    }

    @Override
    /*
     * Scanners are ordered from 0 (oldest) to newest in increasing order.
     */ public List<KeyValueScanner> getScanners(long readPt) throws IOException {
        List<KeyValueScanner> list = new ArrayList<>();
        addToScanners(getActive(), readPt, list);
        addToScanners(snapshot.getAllSegments(), readPt, list);
        return list;
    }

    @Override
    protected List<Segment> getSegments() throws IOException {
        List<Segment> list = new ArrayList<>(2);
        list.add(getActive());
        list.add(snapshot);
        return list;
    }

    /**
     * @param cell Find the row that comes after this one.  If null, we return the
     * first.
     * @return Next row or null if none found.
     */
    Cell getNextRow(final Cell cell) {
        return getLowest(getNextRow(cell, this.getActive().getCellSet()), getNextRow(cell, this.snapshot.getCellSet()));
    }

    @Override
    public void updateLowestUnflushedSequenceIdInWAL(boolean onlyIfMoreRecent) {
    }

    @Override
    protected boolean preUpdate(MutableSegment currentActive, Cell cell, MemStoreSizing memstoreSizing) {
        return true;
    }

    @Override
    protected void postUpdate(MutableSegment currentActive) {
        return;
    }

    @Override
    protected boolean sizeAddedPreOperation() {
        return false;
    }

    @Override
    public MemStoreSize size() {
        return getActive().getMemStoreSize();
    }

    @Override
    public long preFlushSeqIDEstimation() {
        return HConstants.NO_SEQNUM;
    }

    @Override
    public boolean isSloppy() {
        return false;
    }

    /**
     * Code to help figure if our approximation of object heap sizes is close
     * enough.  See hbase-900.  Fills memstores then waits so user can heap
     * dump and bring up resultant hprof in something like jprofiler which
     * allows you get 'deep size' on objects.
     * @param args main args
     */
    public static void main(String[] args) {
        RuntimeMXBean runtime = ManagementFactory.getRuntimeMXBean();
        LOG.info("vmName=" + runtime.getVmName() + ", vmVendor=" + runtime.getVmVendor() + ", vmVersion=" + runtime.getVmVersion());
        LOG.info("vmInputArguments=" + runtime.getInputArguments());
        DefaultMemStore memstore1 = new DefaultMemStore();
        // TODO: x32 vs x64
        final int count = 10000;
        byte[] fam = Bytes.toBytes("col");
        byte[] qf = Bytes.toBytes("umn");
        byte[] empty = new byte[0];
        MemStoreSizing memStoreSizing = new NonThreadSafeMemStoreSizing();
        for(int i = 0; i < count; i++) {
            // Give each its own ts
            memstore1.add(new KeyValue(Bytes.toBytes(i), fam, qf, i, empty), memStoreSizing);
        }
        LOG.info("memstore1 estimated size={}", memStoreSizing.getMemStoreSize().getDataSize() + memStoreSizing.getMemStoreSize().getHeapSize());
        for(int i = 0; i < count; i++) {
            memstore1.add(new KeyValue(Bytes.toBytes(i), fam, qf, i, empty), memStoreSizing);
        }
        LOG.info("memstore1 estimated size (2nd loading of same data)={}",
                memStoreSizing.getMemStoreSize().getDataSize() + memStoreSizing.getMemStoreSize().getHeapSize());
        // Make a variably sized memstore.
        DefaultMemStore memstore2 = new DefaultMemStore();
        memStoreSizing = new NonThreadSafeMemStoreSizing();
        for(int i = 0; i < count; i++) {
            memstore2.add(new KeyValue(Bytes.toBytes(i), fam, qf, i, new byte[i]), memStoreSizing);
        }
        LOG.info("memstore2 estimated size={}", memStoreSizing.getMemStoreSize().getDataSize() + memStoreSizing.getMemStoreSize().getHeapSize());
        final int seconds = 30;
        LOG.info("Waiting " + seconds + " seconds while heap dump is taken");
        LOG.info("Exiting.");
    }
}
